Transmission system



Sept. 4, 1923. 1,466,708

. L. ESPENSCHIED TRANSMI SS I ON SYSTEM Filed Sept. 26 1919 2Sheets-Sheet 1 IN V EN TOR.

E5 ease/lied ATTORNEY Sept. 4, 1923. 1,466,708

L. ESPENSCHIED TRANSMISSION SYSTEM Filed Sept. 26, 1919 2 Sheets-5heet 2nu on. 49 I I IN V EN TOR.

L. Espe/zschfed BY ATT RNEY Patented gent, 4, i923,

teams LIZOYD ESPENQQHIED, OF HOLLIS, NEW YORK, ASSIGNOR TO AMERICANTELEPHONE AND TELEGRAPH COMPANY, A CORPORATION NEW YORK.

TRANSMISSION SYSTEM.

Application filed September 26, 1919. Serial No. 326,523.

To all whom it may concern:

Be it known that L'LLoYn ESPENSCHIED, residing at Hollis, in the countyof Queens and State of New York, have invented certain Improvements inTransmission Systoms, of whichthe following is a specification. v a

This invention relates to transmission systems and more particularly tomultiplex systems employing carrier currents.

Where multiplex transmission is attained by the use of carrier currentsa plurality of carrier frequencies are transmitted over a commontransmission'gline, the carrier frequenciesbeing separated sufficientlyto prevent interference and each frequency being assigned for use as aseparate channel of communicationyso that signals, such for instance, astelephonic variations, may be transmitted by impressing them upon thecarrier frequencies. Several channels may thus be superposed upon acommon transmission line and the line may be thus utilized for multiplextransmission, It is furthermore desirable to transmit over atransniission line in addition to the carrier currents impressed thereonfor telephonic purposes a carrier current or channelwhich may beutilized for signaling, ringing or other purposes and also to providearrangements whereby D. C, Morse or telegraphic currents may besimultaneously transmitted over the line with the carrier currents.

t is a general purpose of this invention to provide arrangements wherebya telephone transmission line of the well-known four-wire type may beutilized for the multiplex transmission of currents for telephonicpurposes, signaling purposes, and telegraphic purposes. A feature of theinvention consists in providingat the two-wire terminals of a four-wireline means for transmitting a low frequency signaling channel over theoutgoing two-wire portion of the four-wire line and means for receivinga low frequency signaling channel transmitted over the incoming two-wireportion of the four-wire lines, these signaling channels in eachinstance causing no interference with the telephonic channels. A furtherfeature of the invention consists'in the rovision of arrangementswhereby D. C. orse 0r telegraphi currents may be transmitted andreceived over both the outgoing and incoming two-wire portions of thefour-wire 'ductors 2 and 3.

line and without causing interference with the telephonic or signalingchannels. Other and further features and objects of the invention willappear more fully from the detailed description hereinafter given.

The invention may be more fully understood with reference to thefollowing description together with the accompanying drawing in theFigures 1 and 2 of which are illustrated circuit diagrams embodying apreferred arrangement of the invention and a. modification thereof.Similar referencenumerals have been used to designate like parts in bothfigures.

In Fig. 1 isillustrated a terminal twowire line of the well-knownfour-wire type of transmission line of which is shown a portion of theincoming line L, thereof and a portion of the outgoing line L thereof,the line L being coupled with line L by means of the three windingtransformer 1, and the line L, being connected to the, mid points ofwindings of transformer 1 by con- Ass ociated with line, L is theartificial line N adapted to balance line L. Included in the lines L,and L are the filter devices F. These filters may be of the typeillustrated in U. S. Patents No. 1,227,113, and 1,227,114 issued to G.A. Campbell, and are designed to readily allow the transmission ofcurrents used for telephonic purposes but which attenuate andpractically extinguish currents of other frequencies, such for purposesof illustration as currents from 0 to 300 cycles. Accordingly by meansof the filters F currents otherithan telephonic currents are'preventedfrom being transmitted from lines L, and L to line L and.thus causingdisturbance in the telephone apparatus associated with line Associatedwith line L, is a receiving circuit for the low frequency signalingcurrents coming in over line L. This receiving circuit is tuned by meansof the arrangements 10 and 11 of inductance and capacity to he resonantto the frequency of the currents for signaling. Accordingly suchcurrents may readily be transmitted over the receiving circuit andcurrents of other frequencies may not be transmitted thereover. In placeof the tuning devices 10 and'll it'is possible to use band filters ifdesired. The receiving circuit includes the rectifier 13, which forpurposesof convenience is shown as of the vacuum bulb type, and thedirect current relay 14'whereby the signal receiving circuit 15 iscontrolled. Associated with line L is a circuit arrangement whereby lowfrequency currents for signaling purposes may be ap plied to line L fortransmission thereover. This signaling current is applied to the signaltransmitting circuit from'the generator 32 which is controlled by relay31 and the includes the devices 10 and 11, similar .to-

circuit 28. The signal transmitting circuit lines L and L aretelegraphic circuits whereby D. C'. Morse or telegraphic currents may betransmitted or received over either of the lines L,- or L The telegraphcircuit associated with line L 'includes the composite sets, 16 and 17and the polar relay 18. The composite sets 16 and 17 are adapted toreadily allow the transmission a of currents having a frequency suitablefor tiff telegraphic puroses but which serve to attenuate and shutoutcurrents of other frequencies; The polar rela 18 controls thereceiving circuit 19 for t e incoming telegraphic lmpulses andby meansof its polarized operation may cause impulses of both positive andnegative polarity to be transmitted over circuit 19. Associated with thetelegraph circuit is the transmitting circuit 20 whereby D. C. Morseimpulses may be transmitted to the telegraph circuit and'out over lineL,. The telegraph circuit. associated with line L, is similar to the oneassociated with linell and includes the composite sets 16 and 17', thepolar relay 27, the telegraph receiving circuit 30, and the telegraphtransmitting circuit 29. ciated with lines L, and L are the networks Nand N respectively which are adapted to balance said lines for purposeswhich will be pointed out later.

The operation of the arrangements illustrated in Fig. 1 is as follows.-Telephonic currents coming in over line L, will be transmitted throughthe filter F and over conductors 2 and 3 and thence over .line L.

'attentuate and practically extinguish such currents. Neither will theseincoming tele phonic currents be transmitted over the tele f graphcircuit associated with line L, as they will be extinguished by thecomposite sets 16 and 17. Tel phonic currents appl edto the ecepoe lineL will be transmitted through transformer '1, through filter F, and outover line L These telephonic currents will not be transmitted over thetelegraph circuit associated with line L as they will be extinguished bythe composite devices 16 and 17 included therein. Accordingly telephoniccurrents either coming in over line L, or transmitted out over line Lwill cause no interference with the signaling or telegraph apparatus ofthe system.

The relatively low frequency currents used for signaling purposes comingin over line L, will not be transmitted through the filter F but will betransmitted over conductors 4: and 5 and thence over conductors 8 and9of the signaling receiving circuit. As has been already pointed out thesignaling receiving circuit is tuned to be resonant to currents of afrequency used for signaling and will readily transmit such currents.These signaling currents will then be transmitted over circuit 12 andthrough the rectifier 13. Connected to the output of the rectifier 13 isthe direct current relay 14: which will be actuated by these signalingcurrents. The relay 14 serves to control the circuit 15 which in turnmay control any desirable signaling apparatus (not shown).

If it is desired to transmit low frequency signaling currents out overthe line L of the four-wire system, the circuit 28 may be 'closed by anysuitable means and current transmitted thereover will operate relay 31.The operation of relay 31 will connect the generator 32 to circuit 33.The generator 32 may be of any desirable type which will generatecurrent havinga frequency suitable for signaling purposes, but it isdesirable to employ a generator giving out as pure a wave form aspossible and Without har monies. This signaling current applied tocircuit 33 will be transmitted, over conductors 25 and 26 of thesignaling transmit ting circuit, which as has been already pointed outis tuned to be resonant to currents of such 'frcquenc and will hencereadily allow, the transmission thereof, and will be 7 transmitted fromconductors 25 and 26 over conductors 23 and 24 and out over line L Thissignaling current applied from conductors 25 and 26 to the conductors 23and 2e 4 and the'conductors 21 and 22 will normally not be transmittedover the telegraph circuit associatedwith line L, as the composite sets16 and 17 are designed to" shut out such current. However if thesignaling current was of such a character that a portion thereof shouldleak through the composite set 17 each other and accordingly would noteffect polar relay 27. Furthermore these signaling currents transmittedfrom conductors 25 and 26 to conductors 21 and 22 andthe conductors 23and 24 would normally be extinguishedby the filters F in line L andhence would not be transmitted through transformer 1 and out over lineL. However, if the signaling current generated contained harmonics ofthe original wave and such harmonics were of afrequency within thetelephonic range, aportion of the signaling currents would betransmitted through both of the filters F. However these currents wouldbe opposite and ap-' proximately equal and at'po'ints 36 and 37 wouldbalance and neutralize each other and hence would notbe transmittedthrough trans former 1 and out over line L. In order to insure thatthese currents will be approximately equal the network N is rovidedwhich is adapted to simulate line in impedance value. In a similarmanner the con ductors (Sand 7 V are provided associated:

with the line L and the signaling receiving circuit associated with saidline in order to neutralize andbalance any of the telegraph currentstransmitted over line L which might leak through the filters F in sthhline. Accordingly the arrangements of the invention provide a means forreceiving signaling currents coming in over one side of the four-wireline and transmitting signaling currents out over the otherfside of thefourwire line without causing any interference between them andtelephonic or telegraphic circuits associated therewith.

If it is desired to transmit D. C. Morse or telegraphic currents outover line L,, such currents maybe applied to circuit 20-and thence tothe telegraph circuit associated therewith. These currents will readilybe transmitted over the telegraph circuit as the composite devices 16and 17 aredesigned toallow the transmission of currents used fortelegraph purposes. These telegraph currents will then be applied to theconductors 6 and 7 and to conductors 4 and 5. From conductors 4 and 5the telegraph currents will be transmitted out over line L,. Normallythese telegraph'currents will not be transmitted over: line L as theywill be shut out' by filter F. -Neither will these currents betransmitted over the signaling receiving circuit as the tuning devices10 and 11 therein will render such circuit an inetlicient path for thetransmission of such currents. However an of such --telegraph currentswhich might. be asto-be transmitted from conductors 4 and 5 eitherthrough the tuning device 10 or the filter F would be neutralized byequal and opposite balancing currents which. would be transmitted fromconductors 6' and and through the tuning device 11 or the leftof such anature hand filter F. Accordingly'telegraphic currents may betransmitted out over line L without causing any disturbance with thetelephonic or signal ng arrangements of the system.

Telegraphic currents coming in over line L would be attenuated andextinguished by filter F and tuning device 10 and would be transmittedover conductors 4 and 5 and through composite set 17 and-would actuatethe polarized relay -18. The polarity of the incomingtelegraphiccurrents would determine the operation of polar relay. 18 andupon the operation of this relay current of either polarity-may betransmitted over the circuit 19 to apparatus (not shown) associatedtherewith and adapted to receive the telegraphic impulses. Associatedwith the telegraph circuit are thebalancing conductors 6 and 7 which inthe same manner as pointed .out with respect to the'signaling receivingcircuit will serve to neutralize and balance any of the telegraphicimpulses which may not be properly shut out by filter F or the tuningdevice 10, and accordingly an additional safeguard is provided. againstinterference with the telephonic-or signaling arrangementsv from thetelegraph apparatus. As the arrangements for transmitting andreceivingtelegraphic impulses over line L are sol substantially similar to thosedescribed with respect to line L no further description thereof willbegi'ven.

In Fig. 2 is illustrated a modification of the arrangements illustratedin Fig. 1, in which a slightly difierent circuit arrangement is'shown,similar numerals indicating like parts in both figures of.the.invention. The incoming twowire line L ofth fourwire system iscoupled through trans ormer 39' to the conductors 2 and.3, which areconnected to the terminal two-wire line. L. The line, L terminates inthe network N,,

adapted to balance saidline. The outgoing two-wire line L,, of thefour-wire system, is coupled to the terminal two-wire line L inthe-usual manner through the three-wire transformer 1. Included inconductors 2 and 3, and in conductors 2' and 3-, are the filters F,adapted to readily allow thetransmission of currents having a frequencysuit- .of. frequencies which may be applied either to the line L, or tothe line L will not be transmitted over the line l), as they will beeffectually attenuated by the filters F, and accordingly such currentswill cause no interference with the telephonic apparatus associated withline L. Associated with line L is a low frequency signaling receivingcircuit terminating in circuit 15, adapted to receive the low frequencysignaling currents coming in over line L,. Associated with line L is atelegraphic circuit, with which are associated the circuits '19 and 20,whereby currents suitable for telegraphic purposes may either bereceived from the line L or transmitted out over the line L,. Associatedwith line L is a low frequency signaling transmitting circuit,terminating in the circuit 28, whereby low frequency signaling currentsmay be transmitted out over the line L Associated with line L is atelegraphic circuit, with which are associated the circuits 29 and 36,whereby currents suitable for telegraphic purposes may either hereceived over the line L, or transmitted out over the line L The lowfrequency signaling receiving circuit associated with line L includesthe tuning devices 10 and 11, which serve to make the circuit resonantto the low frequency currents used for signaling purposes. Accordinglythis circuit will readily allow the transmission of suchcurrents, butwill attenuate and extinguish currents of other frequencies. In asimilar manner the low frequency signaling trans- -mitting currentassociated with line 2 incordingly the signaling currents coming in overthe L, will cause no interference with the telephonic apparatusassociated with the line L. These incoming signaling currents,furthermore, will cause no interference in the telegraphic circuitassociated with line L, as they will normally be attenuated andextinguished by the composite sets 16 and 17 included therein.Furthermore, the balancing conductors 6 and 7 are provided so that anyof the incoming sig naling currents, which might be transmitted throughthe composite set 17, would be opposed and neutralized by equal and opposite currents which would have been transmitted over the balancingconductors 6 and 7 and through composite set 16. Included in conductors6 and i? is the tuning device essence 39, similar to the tuning device10, in order to balance the tuning device 10. Low frequencies signalingcurrents transmitted over circuit 28, and thence out over the line Lwill normally cause no interference with the telegraphic apparatusassociated with the line L as such currents will be extinguished by thecomposite sets 16' and 17. Furthermore, the balancing conductors 21 and22 are provided, over which equal and opposite currents may betransmitted to neutralize any of the signaling currents which might betransmitted over conductors 23 and 24 and through the composite set 17.The conductors 21 and 22 include the tuning device 40, adapted tobalance the tuning device 10. Associated with the telegraphic circuitsare the additional compo'site sets 40.

and 41. In other respects the telegraphic circuits associated with thelines L and L, are substantially the same as already described withrespect to Fig. 1, and no description thereof will be given.

While the invention has hen disclosed in certain specific arrangementswhich have been deemed desirable, it is understood that it is capable ofembodiment in many and widely varied forms without departing from thespirit of the invention as defined by the appended claims. For example,the circuit which has been referred to above and is specified in theclaims below as a signaling channel may be used for carrier oralternating current telegraph transmission as well as for signaling ofthe type incident to telephone operating.

What is claimed is:

1. The combination of a four-wire tran mission system including anincoming twowire line and an outgoing two-wire line and a terminaltwo-wire line and arrangements whereby said system may be utilized forthe simultaneous transmission of currents for purposes of telephoning,telegraphing and signaling, said arrangements comprising a circuitassociated with said incoming two-wire line and adapted to efficientlytransmit signaling currents coming in over said line, signalingapparatus controlled by said circuit, means in said circuit forpreventing telephonic currents coming in over said two-wire line frombeing transmitted over said circuit, and means in said incoming two-wireline for preventing signaling currents coming in over said line frombeing transmitted from said line to said terminal line.

2. The combination of a four-wire trans mission system including anincoming twowire line and an outgoing two-wire line and a terminaltwo-wire line and arrangements whereby said system may be utilized forthe simultaneous transmission of currents for purposes of telephoning,telegraphing and signs-Ming, said arrangements comprising,

needs/cs a circuit associated with said incoming two wire line andadapted to efiiciently transmit signaling currents coming in over saidline, signaling apparatus controlled by said circuit, means in saidcircuit for preventing telephonic currents coming in over said two-wireline from being transmitted over said circuit, means in said incomingtwowire line for preventing signaling currents coming in over said linefrom being transmitted from said line to said terminal dine, a circuitassociated with said outgoing twowire line and adapted to 'eflicien-tlytransmit currents suitable for signaling purposes, means for applyingsignaling currents to said circuit for transmlssion out over saidoutgoing two-wire line, means in said circuit for preventing *telephoniccurrents transmitted over said outgoing line from being transmitted oversaid circuit, and means in said outgoing line for preventing thesignaling currents applied thereto from bein transmitted from said lineto said ter-' mina line.

3. A four-wire transmission arranged for' the simultaneous transmissionover the four-wire portion thereof of currents for telephonic purposes,for signal-i ing purposes, and for telegraphic purposes, meansassociated with the four-wire portions said system at the terminalsthereof for preventing the telephonic currents from interfering with theslgnaling or telegraphic apparatus of the system, means associatcd withthe four-wire portions of said system at the terminals thereof forpreventing the signaling currents from interfering with the telephonicor telegraphic apparatus of the system, and means associated with thefour-Wire portions of said system at the terminals thereof forpreventing the telegraphic currents from interfering with the telephonicor signaling apparatus of the system.

t. lhe combination of a four-wire transmissionsystem including anincoming twowire line and an outgoing two-wire line and a terminaltwo-wire line and arrangementswhereby said system may be utilized forthe simultaneous transmission of currents for purposes of telephoning,telegraphing and signaling, said arrangements comprising a circuitassociated with said incoming twowire line and tuned to be resonant tosignalin currents coming in over said line, signa ing means controlled'by said circuit, a secon circuit associated with incoming two-wireline, composite sets in said second circuit adapted to readily allow thetransmission of telegra hic currents and to shut out currents use fortelephonic or slgnaling purposes, a telegraph receiving circuit and atelegraph transmitting circuit associated with said second circuit, anda filter included in said incoming two-wire line adapted to readilyallow the transmission of telephonic currents and to attenuate andextinguish telegraphic and signaling currents.

5. The combination of a four-Wire transmission system including anincoming two- Wire line and an outgoing two-wire line and a terminaltwo-wire line and arrangements whereby said system may be utilized forthe simultaneous transmission of currents for purposes of telephoning,telegraphing and signaling, said arrangements comprising, a circuitassociated with said incoming two wire line and tuned to be resonant tosignalin currents coming in over said line, signaling means controlledby said circuit, a second circuit associated with said incoming two-wireline, composite sets in said second circuit adapted to readily allow thetransmission of telegraphic currents and to shut out currents used fortelephonic or signaling urposes, a telegraph receiving circuit an atelegraph transmitting circuit associated with said second circuit, afilter included in said incoming two-wire line adapted to readilyallowthe transmission of telephonic currents and to attenuate and extinguishtelegraphic and signaling currents, a circuit associated with saidoutgoing twowire line and tuned to be resonant to signaling currentstransmitted out over said line, means for applying signaling currents tosaid circuit and out over said outgoing two-Wire line, a second circuitassociated with said outgoing two-wire line, composite sets in said lastmentioned second circuit adapted to readily allow the transmission oftelegraphic currents and to shut out currents used for telephonic orsignaling purposes, a telegraph receiving and a telegra h transmittincircuit associated with sai last mentione second circuit, and a filterincluded in-said outgoing two-wire line adapted to readily allow thetransmission of telephonic current and toattenuate and extin ishtelegraphic and signaling currents.

l rl testimony whereof, I have signed my name to this specification this25th. day at September 1919.

morn nsrnnscmsn.

